The present invention relates to a polymer dispersion composition obtained by dispersing a polymer in an organic dispersion medium. The polymer dispersion composition is successfully usable as a binder composition for batteries. Accordingly, the present invention also relates to a slurry composition for batteries using said polymer dispersion composition as a binder composition for batteries, and to an electrode and a battery using the same.
An elastomer is a soft polymer having rubber elasticity of which glass transition temperature is 30xc2x0 C. or below. Such elastomers are in use in various fields.
An elastomer is used for forming a uniform film by the procedure of (1) melting, followed by coating, (2) forming a uniform solution by dissolution in an organic solvent, followed by coating, (3) forming a stable dispersion in an aqueous solvent by the use of a surfactant, followed by coating, etc. Although JP-A, 6-179707 proposes a method of dispersing an elastomer in an aqueous or organic solvent without using surfactant, the examples presented in the specification thereof are limited to those using an aqueous solvent, and the films formed by the use of an organic solvent are considered a homogeneous films. Thus, there is known no case of using an elastomer dispersion composition prepared by dispersing an elastomer in an organic dispersion medium for formation of a heterogeneous film having a high gel content or for a general binder.
A battery has positive and negative electrodes as the constituent elements thereof. An electrode is constituted of a variety of elements including an active material participating in electrochemical reaction, an electrode base, electroconductive particles as optional constituents, etc. An electrode is prepared by mixing an active material, etc. with a binder composition, etc. to form a slurry composition for batteries, coating the slurry composition onto an electrode base, and drying it. A slurry composition for batteries is prepared by adding an active material to a binder composition comprising a binder polymer and a solvent or a dispersion medium.
The prior binder compositions for batteries are classified into those of organic solvent type and those of aqueous solvent type. Most of the conventional organic solvent type of binder compositions for batteries are solution type binder compositions prepared by uniformly dissolving polyvinylidene fluoride in N-methylpyrrolidone which is a polar organic solvent (for example, see: JP-A, 4-249860), and there is known no case of using an elastomer dispersion composition prepared by dispersing an elastomer in an organic dispersion medium as a binder composition for batteries.
The prior organic solvent type binder compositions are free from the faults of the aqueous binder compositions mentioned below, because they are of organic solvent type. However, the uniform film formed from the homogeneous solution comes to cover the whole surface of electrode active material, which is undesirable under the present conditions of matters where enhancement of the capacity of battery is desired, because such a uniform film decreases the surface area of active material coming into a direct contact with electrolyte. It is desired to enlarge the proportion of active material contributing to electric capacity of active material, namely to enlarge the surface area of active material coming into contact with electrolyte.
As aqueous binder compositions, there have been proposed those prepared by adding carboxymethyl cellulose as a thickener to an aqueous dispersion of styrene-butadiene copolymer rubber latex prepared by emulsion polymerization using a surfactant (for example, JP-A, 4-342966, JP-A, 5-21068, JP-A, 5-74461, etc.). This type of binder compositions have a problem that, when used in a lithium ion secondary battery or the like, the contact with water causes formation of hydroxyl groups linked to active material surface which can exercise an influence of lowering the initial capacity. Further, there is a problem that, in a non-aqueous battery of lithium type using a non-aqueous electrolyte, the contact with water must be avoided as possible from the viewpoint of improving the efficiency of manufacture, even though the battery manufacturing process may include a drying step.
The present inventors have succeeded in preparing a polymer dispersion composition by dispersing a specified polymer in a specified organic dispersion medium, and have found that the polymer dispersion composition thus obtained can successfully be used as a binder composition for batteries. Based on the finding, the present invention has been accomplished.
(Polymer Dispersion Composition)
Accordingly, an object of the present invention is to provide a polymer dispersion composition wherein a specified polymer is dispersed in a specified organic dispersion medium, to use the polymer dispersion composition as, for instance, a binder composition for batteries, to suppress the deteriorating quality of active material caused by water, to make it possible to fix an electrode active material on an electrode in a partially exposed state without coating the whole surface of the electrode active material, and thereby to make small the extent of damage in the function of active material. It is a further object of the invention to fix a large quantity of active material on an electrode base by the use of such a binder composition for batteries and thereby to provide a battery having a high initial capacity and prevent the release of active material from electrode base even after repeated charge and discharge cycle.
Thus, according to the present invention, there are provided a polymer dispersion composition obtained by dispersing a polymer having a gel content of 50% or more in an organic dispersion medium having a boiling point of 80xc2x0 C. or above at 760 mmHg, a slurry composition for batteries obtained by mixing said composition with an electrode active material, an electrode obtained by coating said slurry composition for batteries onto the surface of a battery base and then removing the organic dispersion medium, and a battery using said electrode.
The organic dispersion medium used in the present invention has a boiling point of 80xc2x0 C. or above, preferably 100xc2x0 C. or above, at 760 mmHg. When used as a binder composition for batteries, the organic dispersion medium preferably has a boiling point of 150xc2x0 C. or below at 760 mmHg and a boiling point of 300xc2x0 C. or below at 760 mmHg, because it is necessary to dry an electrode base without deterioration thereof. If the boiling point at 760 mmHg is lower then 80xc2x0 C., the drying progresses too rapidly so that coating of the electrode base is difficult to carry out; and the polymer migrates and is concentrated into the surface of electrode base during the drying step to cause problems such as deterioration of film strength, decrease of binding force between electrode active material particles, etc. These problems arise especially when the organic dispersion medium is an alcohol or a ketone of which boiling point is lower than 80xc2x0 C., such as ethyl alcohol.
As concrete examples of the organic dispersion medium, there can be referred to a variety of polar and non-polar dispersion mediums including aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene and the like; aliphatic hydrocarbons such as heptane, octane, nonane, decane and the like; alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, ethylcyclohexane and the like; ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, cycloheptanone and the like; cyclic and acyclic amides such as dimethylformamide, N-methyl-pyrrolidone and the like; alcohols such as butyl alcohol, amyl alcohol, hexyl alcohol and the like; esters such as methyl lactate, ethyl lactate, butyl lactate, butyl acetate, methyl benzoate and the like; etc. In a case where the composition is used as a binder composition for batteries, those having a boiling point of 100 to 250xc2x0 C. at 760 mmHg are especially preferably selected from cyclic and acyclic amides, ketones, esters and aromatic hydrocarbons because these dispersion mediums are well-balanced between polymer-dispersing performance, easiness of handling, safety, easiness of synthesis, etc.
The polymer used in the present invention is a polymer having a gel content of 50% or more. This polymer is preferably a polymer prepared by using, as the first component monomer, a monomer which gives an elastomer, namely a soft polymer having a rubber elasticity and a Tg of 30xc2x0 C. or below, when converted to a homopolymer. Of these monomers, conjugated dienes and ethylenically unsaturated carboxylic ester type monomers are preferably used for polymerization. Mechanism of the polymerization is usual radical polymerization or ionic polymerization, and the polymerization reaction may be carried out by any of usual methods such as emulsion polymerization, suspension polymerization, solution polymerization, etc. The polymer used in the present invention may be either a homopolymer of a conjugated diene monomer or an ethylenically unsaturated carboxylic ester type monomer or a copolymer of a conjugated diene monomer and an ethylenically unsaturated carboxylic ester monomer. Owing to the use of these monomer components, the polymer can be given an elastomeric properties as a whole or partially. As used herein, the term xe2x80x9celastomeric propertiesxe2x80x9d means adhesiveness, softness, etc. When the composition is used as a binder composition for electrodes of secondary batteries, especially important properties are adhesiveness to electrode base on electrodes and softness (elongation and permanent elongation) enough to cope with the movement of active material at the time of charge and discharge.
Further, a second component different from the first component may be used. As said second component, ethylenically unsaturated monomers other than the above-mentioned ethylenically unsaturated monomers giving an elastomer when converted to a homopolymer can be used, of which examples include ethylenically unsaturated carboxylic acid monomers, styrene monomers, nitrile group-containing monomers, acrylamide monomers, methacrylamide monomers, glycidyl group-containing monomers, sulfonic acid group-containing monomers, amino group-containing monomers, and the like.
As concrete examples of the conjugated diene monomers used as the first component, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, piperylene and the like can be referred to.
As concrete examples of the ethylenically unsaturated carboxylic ester monomers used as the first component, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, lauryl acrylate, lauryl methacrylate, methyl crotonate, ethyl crotonate, ethyl isocrotonate and the like can be referred to.
The second component is as follows. (1) As concrete examples of the ethylenically unsaturated carboxylic acid monomer, ethylenically unsaturated carboxylic ester monomers giving no elastomer when converted to a homopolymer such as methyl methacrylate and ethyl methacrylate; unsaturated monocarboxylic acid monomers such as acrylic acid, methacrylic acid and the like; unsaturated dicarboxylic acid monomers such as maleic acid, fumaric acid, citraconic acid, methaconic acid, glutaconic acid, itaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid, nadic acid and the like; and monoesters of ethylenically unsaturated carboxylic acids such as monooctyl maleate, monobutyl maleate, monooctyl itaconate and the like can be referred to. (2) As concrete examples of the styrene monomers, styrene, xcex1-methylstyrene, xcex2-methylstyrene, p-t-butylstyrene, chlorostyrene and the like can be referred to. (3) As concrete examples of the nitrile group-containing monomers, acrylonitrile and methacrylonitrile can be referred to. (4) As concrete examples of the acrylamide type monomers, acrylamide, N-methylolacrylamide, N-butoxymethylacrylamide and the like can be referred to. (5) As concrete examples of the methacrylamide type monomers, methacrylamide, N-methylolmethacrylamide, N-butoxymethylmethacrylamide and the like can be referred to. (6) As concrete examples of the glycidyl group-containing monomers, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether and the like can be referred to. (7) As concrete examples of the sulfonic acid group-containing monomers, sodium styrene-sulfonate, acrylamidomethylpropane-sulfonic acid and the like can be referred to. (8) As concrete examples of the amino group-containing monomers, dimethylaminoethyl methacrylate, diethylamino-ethyl methacrylate and the like can be referred to.
As the second component, ethylenically unsaturated carboxylic acid type monomers, styrene type monomers and nitrile group-containing monomers are preferred.
In cases where a second component is used, the proportion thereof is usually from 1:0.1 to 1:10 and preferably from 1:0.5 to 1:5, as expressed in terms of ratio (by weight) of the first component to the second component.
The use of a second component is desirable because the binding force between a binder composition for batteries and a metal constituting an electrode base can be enhanced by its use. Further, if an unsaturated dicarboxylic acid type monomer or a nitrile group-containing monomer is used, polymer becomes easier to disperse when N-methylpyrrolidone or the like is used as an organic dispersion medium. The proportion of the unsaturated dicarboxylic acid type monomer or nitrile group-containing monomer is not smaller than 5% by weight, preferably not smaller than 10% by weight, and not larger than 90% by weight, preferably not larger than 60% by weight and further preferably not larger than 30% by weight, based on the total monomers. Since the use of an excessively large amount of the second component causes deterioration of the softness of polymer, such a binder composition for batteries can make the electrode active material easily releasable.
As concrete examples of such a polymer, there can be referred to homopolymers and copolymers of conjugated diene monomers, copolymers of a conjugated diene monomer and an ethylenically unsaturated carboxylic ester type monomer, homopolymers and copolymers of ethylenically unsaturated carboxylic ester type monomer, copolymers obtained by using a conjugated diene monomer and an ethylenically unsaturated carboxylic ester type monomer as first components and a styrene type monomer as a second component, copolymers obtained by using a conjugated diene monomer and an ethylenically unsaturated carboxylic ester type monomer as first components and an unsaturated dicarboxylic acid type monomer and a styrene type monomer as second components, copolymers obtained by using a conjugated diene monomer and an ethylenically unsaturated carboxylic ester type monomer as first components and an unsaturated dicarboxylic acid type monomer, a styrene type monomer and a nitrile group-containing monomer as second components, and copolymers obtained by using an ethylenically unsaturated carboxylic ester type monomer as first component and an unsaturated carboxylic acid monomer, an unsaturated carboxylic ester type monomer and a styrene type monomer as second components, etc. More specifically saying, examples of such a polymer include polybutadiene, polyisoprene, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-butadiene-methyl methacrylate copolymer, styrene-acrylonitrile-butadiene copolymer, styrene-acrylonitrile-butadiene-methyl methacrylate copolymer, styrene-acrylonitrile-butadiene-methyl methacrylate-itaconic acid copolymer, styrene-acrylonitrile-butadiene-methyl methacrylate-fumaric acid copolymer, polystyrene-polybutadiene block copolymer, and the like.
Of these polymers, preferred are those prepared by using butadiene as the conjugated diene monomer, butyl acrylate as the ethylenically unsaturated carboxylic ester type monomer, acrylic acid as the unsaturated monocarboxylic acid monomer, itaconic acid or fumaric acid as the unsaturated dicarboxylic acid monomer, methyl methacrylate as the unsaturated carboxylic ester type monomer, styrene as the styrene type monomer, and acrylonitrile as the nitrile group-containing monomer.
The polymer used in the present invention has a form of particle which can be dispersed in a dispersion medium. Particle diameter thereof, determined by vaporizing off the dispersion medium, thereafter measuring major and minor diameters of 100 particles by means of electron microscope and calculating a mean value thereof, is usually from 0.005 to 100 xcexcm and preferably from 0.01 to 50 xcexcm. If the particle diameter is too large, the composition using such a polymer as a binder composition for batteries is insufficient in contact with electrode active material, due to which the inner resistance of electrode increases. If the particle diameter is too small, an excessively large quantity of binder must be used, due to which the surface of active material is covered with the binder.
Gel content of the polymer used in the present invention is usually 50% or more, preferably 75% or more, and further preferably 80% or more. In the present invention, gel content is expressed by toluene-insoluble fraction, which is determined by drying about 1 g of polymer at 100xc2x0 C. for 24 hours, measuring the weight in dryness, dipping the dry polymer in toluene for 24 hours at ambient temperature of 25xc2x0 C., sifting the polymer through a 200 mesh sieve, drying the solid remaining on the sieve, measuring the weight of dry polymer, and calculating the gel content according to the following formula:
xe2x80x83(weight of dry solid remaining on the sieve/weight of dry polymer)xc3x97100
A gel content represents the extent of cross-linking of a polymer. A polymer having a gel content smaller than 50% is undesirable, because such a polymer is soluble in organic dispersion medium and, when used as a binder composition for batteries, such a polymer coated on an electrode base spreads and covers the surface of active material and thereby decreases the contribution of active material to the electric capacity.
Cross-linking is usually necessary for gelation of the polymer mentioned above. The cross-linking may be a self-crosslinking caused by heat, light, radiation, electron beam or the like, or may also be a cross-linked structure introduced by the use of a cross-linking agent. Combination of these two modes of cross-linking may also be adopted.
As examples of the cross-linking agent, there can be referred to various cross-linking monomers including peroxide type cross-linking agents such as benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(peroxidobenzoato)hexyne-3,1,4-bis(tert-butylperoxyisopropyl)benzene, lauroyl peroxide, tert-butyl peracetate, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3,2,5-trimethyl-2,5-di(tert-butylperoxy)hexane, tert-butylperbenzoate, tert-butyl perphenylacetate, tert-butyl perisobutyrate, tert-butyl per-sec-octoate, tert-butyl perpivalate, cumyl perpivalate, tert-butyl perdiethylacetate and the like; azo compounds such as azobisisobutyronitrile, dimethyl azoisobutyrate and the like; dimethacrylate compounds such as ethylene diglycol dimethacrylate, diethylene diglycol dimethacrylate and the like; trimethacrylate compounds such as trimethylolpropane trimethacrylate and the like; diacrylate compounds such as polyethylene-glycol diacrylate, 1,3-butyleneglycol diacrylate and the like; triacrylate compounds such as trimethylolpropane triacrylate and the like; divinyl compounds such as divinylbenzene and the like; etc. Of these cross-linking agents, preferred are dimethacrylate compounds such as ethylene diglycol dimethacrylate and the like and divinyl compounds such as divinylbenzene and the like.
When a lumpy polymer of cross-linked structure is formed, such a material may be put to use after cooling it to a temperature lower than Tg, followed by pulverizing by means of jet mill.
The polymer dispersion composition of the present invention is obtained by, for example, preparing an aqueous dispersion of a polymer in an aqueous dispersion medium and then exchanging the dispersion medium from the aqueous dispersion medium to an organic dispersion medium. When this method is adopted, the water must be removed. In cases where boiling point of the organic dispersion medium used is higher than boiling point of water, an organic dispersion medium is added and thereafter water is evaporated off by the use of an evaporator or the like. In cases where the organic dispersion medium is a material capable of forming an azeotropic mixture with water, the organic dispersion medium is added and then the quantity of water is decreased to some extent by azeotropic distillation using an evaporator or the like, and thereafter the residual water is removed by the use of a water-absorbent such as molecular sieve or by means of reverse osmotic membrane.
As another method for producing the polymer dispersion composition of the present invention, there can be referred to a method of producing a polymer in an aqueous dispersion medium, coagulating, drying and pulverizing the polymer dispersion thus formed, and dispersing the pulverized polymer in an organic dispersion medium, and a method of producing a polymer in an aqueous dispersion medium, coagulating and drying the polymer thus formed, mixing the polymer with an organic dispersion medium, and then pulverizing the mixture. The dispersing treatment can be achieved with conventional dispersing machines such as ball mill and sand mill, or with ultrasonic dispersing machine, homogenizer, or the like.
In a case where a polymer is produced in an organic dispersion medium and the polymer thus formed is a lumpy material, a polymer dispersion composition dispersed in the organic dispersion medium can be obtained by pulverizing the lumpy polymer by means of ball mill, sand mill or the like.
(Binder Composition for Batteries)
A variety of additives may be added to the polymer dispersion composition of the present invention according to the use thereof.
For instance, the polymer dispersion composition is successfully usable as a binder composition for batteries. When the composition of the present invention is put to such a use, a viscosity regulator may be additionally added for the purpose of facilitating the procedure for obtaining a coating film of desired thickness. As the viscosity regulator, there can be used polyvinylpyrrolidone, polyacrylic acid, polymethacrylic acid, polyacrylamide, poly-N-isopropylacrylamide, poly-N,N-dimethylacrylamide, polyethyleneimine, polyoxyethylene, poly(2-methoxyethoxyethylene), polyvinyl alcohol, poly(3-morpholinylethylene), polyvinylsulfonic acid, polyvinylidene fluoride, polysaccharides such as amylose, amylopectin, starch and the like and cellulosic compounds such as carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxyethyl methyl cellulose and the like.
When the composition of the present invention is used as a binder composition for batteries, concentration of the polymer dispersed in the organic dispersion medium is from 0.1 to 70% by weight, preferably from 1 to 60% by weight, and further preferably from 2 to 50% by weight. If concentration of the polymer is too low, the slurry composition for batteries prepared therefrom is difficult to adjust to a concentration at which the composition can easily be coated onto electrode base. If concentration of the polymer is too high, the polymer tends to agglomerate in the organic dispersion medium.
(Slurry Composition for Batteries)
A slurry composition for batteries of the present invention is prepared by adding an electrode active material to the binder composition for batteries mentioned above.
As the active material, those used in the usual batteries can be used. For instance, in the case of lithium battery, carbon fluoride, graphite, natural graphite, PAN type carbon fibers such as MCMB and the like, carbonaceous materials such as pitch type carbon fiber and the like, electrically conductive polymers such as polyacene and the like, lithium nitride compounds such as Li3N and the like, lithium type metallic materials such as lithium metal, lithium alloy and the like, metallic compounds such as TiS2, LiTiS2 and the like, metallic oxides such as Nb2O5, FeO, Fe2O5, Fe3O4, CoO, Co2O3, Co3O4 and the like, and composite metallic oxides represented by AxMyNzO2 wherein A is Li, M is at least one member selected from the group consisting of Co, Ni and Mn, N is at least one member selected from the group consisting of Al and Sn, O is oxygen atom, and X, y and z are numerical figures satisfying the following formulas:
1.10xe2x89xa7xxe2x89xa70.05
4.00xe2x89xa7yxe2x89xa70.85
and
2.00xe2x89xa7zxe2x89xa70
can be used as a negative electrode active material; and inorganic compounds such as oxides, sulfides and selenides of manganese, molybdenum, vanadium, titanium, niobium and the like, lithium-containing composite oxides such as lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide and the like, TiS2, TiS3, amorphous MoS3, Cu2V2O3, amorphous V2O5xe2x80x94P2O5, MoO3, V2O5, V6O13, composite metallic oxides represented by AxMyNzOp wherein A is Li, M is at least one member selected from the group consisting of Co, Ni and Mn, N is at least one member selected from the group consisting of Al and Sn, O is oxygen atom, and x, y, z and p are numerical figures satisfying the following formulas:
1.10xe2x89xa7xxe2x89xa70.05
4.00xe2x89xa7yxe2x89xa70.85
2.00xe2x89xa7zxe2x89xa70,
and
5.00xe2x89xa7pxe2x89xa71.5,
electrically conductive polymers such as polyacetylene, poly-p-phenylene and the like, etc. can be used as the positive electrode active material.
Although the amount of active material in the slurry composition for batteries is not particularly limited, the active material is added in an amount of usually 1 to 1,000 times, preferably 5 to 1,000 times, further preferably 10 to 1,000 times, and especially preferably 15 to 100 times as much as the amount of the polymer, all by weight. If the amount of the active material is too small, many inactive portions are formed in the active material layer on the electrode base, which makes the function of electrode insufficient. If the amount of the active material is too large, the active material cannot be sufficiently fixed onto the electrode base and is readily releasable. If desired, an organic dispersion medium may be added to the slurry composition for batteries for the purpose of adjusting the slurry to a concentration at which the composition can easily be coated onto the electrode base.
(Electrode)
An electrode of the present invention is obtained by coating the slurry composition for batteries mentioned above onto an electrode base and removing the organic dispersion medium, by which the active material is immobilized in the matrix thus formed on the electrode base surface.
Although the electrode base is not particularly limited in material so far as it is made of an electrically conductive material, it is usually made of a metal such as iron, copper, aluminum or the like. Although the shape thereof is not particularly limited, the electrode base usually has a sheet-like shape having a thickness of about 0.01 to 0.5 mm.
The method for coating the slurry composition for batteries onto the electrode base is not particularly limited. For instance, the slurry composition can be coated by the method of dipping, brushing, etc. Although the quantity of the slurry composition for batteries to be coated is not particularly limited, it is such a quantity that thickness of the active material layer formed after removing the organic dispersion medium becomes 0.01 to 5 mm and preferably 0.1 to 2 mm. Although the method for removing the organic dispersion medium is not particularly limited, the organic dispersion medium is usually removed while controlling the extents of evacuation and heating so as to vaporize the organic dispersion medium as speedily as possible within a speed range where no crack is formed in active material layer due to concentrated stress and no peeling of active material layer from electrode base takes place.
(Battery)
In the battery of the present invention, the above-mentioned electrode is used as at least one of positive electrode and negative electrode. Although the battery may be any of a battery using an aqueous electrolytic solution and a battery using a non-aqueous electrolytic solution, an especially excellent battery performance can be exhibited when the electrode is used for a battery using a non-aqueous electrolytic solution. As batteries using non-aqueous electrolytic solution, there can be referred to lithium type batteries such as lithium primary battery, lithium metal secondary battery, lithium ion secondary battery, lithium polymer secondary battery, lithium ion polymer secondary battery and the like.
The electrolytic solution in the lithium type battery is not particularly limited, but those exhibiting a battery performance may be selected in accordance with the kinds of negative electrode active material and positive electrode active material. For instance, as the electrolyte, the electrolytes conventionally used in lithium batteries such as LiClO4, LiBF4, CF3SO3Li, LiI, LiAlCl4, LiPF6 and the like can be referred to. As solvent for the electrolyte, ethers, ketones, lactones, nitrites, amines, amides, sulfur compounds, chlorinated hydrocarbons, esters, carbonates, nitro compounds, phosphoric ester compounds, sulfolane compounds and the like can be referred to. Of these solvents, carbonates such as ethylene carbonate and diethyl carbonate are suitably usable generally.